A lateral flow assay (“LFA”) can be a paper-based device that detects a presence of an analyte in a sample without the need for costly equipment. LFAs are a common point of care diagnostic tool.
LFAs function by wicking (e.g., capillary action) a sample of interest through a porous membrane (e.g. paper) where chemical reactions can occur in and on the surface of the porous membrane. The LFA can contain a conjugate material therein. Conjugate materials are typically formulated to provide the solvent(s) and reactant(s) necessary to dissolve, react, color, tag, or bond to the suspected analyte in a sample. Thus, if the analyte is present, the conjugate or a component thereof will react with the analyte in the sample. The conjugate can include a taggant or other material configured to provide a visual indication of the presence of the analyte, reacted analyte, or analyte-conjugate complex. Typically, the readout of an LFA is a visual change at some point along a length of the LFA. Many LFAs include an analyte collection material near the distal end of the LFA whereby the analyte and any taggant bonded thereto are bound in large concentration to provide visual indication of a positive or negative result.
LFAs can have limited flow control so that once the liquid enters a LFA, the liquid continues flowing through capillary action at a predetermined rate at least partially governed by the Lucas-Washburn equation. Without flow control, the complexity of chemical reactions that can be carried out in an LFA is limited.